Hydrofoils and retraction mechanism therefor



Sept. 26, 1967 J. BADER 3,343,513

HYDROFOILS AND RETRACTION MECHANISM THEREFOR Filed May 27, 1966 a Sheets- Sheet 1 .i j 3 3 it O; O 2 Cu O x LLI 2 3 [I U 19 3 IO w N ,J H m m IN I INVENTOR JOHN 5405/? ATTORNEY J. BADER Sept. 26, 1967 HYDROFOILS AND RETRACTION MECHANISM THEREFOR Filed May 27, 1966 3 Sheets-Sheet 2 INVENTOR JOHN BAUER TTORNEY Sept. 26, 1967 J. BADER 3,343,513

HYDROFOILS AND RETRACTION MECHANISM THEREFOR Filed May 27, 1966 3 Sheets-Sheet 5 FIG. 3 MENTOR JOHN BA DEF? ATTORNEY United States Patent ()fifice 3,343,513 Patented Sept. 26, 1967 3,343,513 HYDROFOILS AND RETRACTION MECHANISM THEREFOR John Bader, Montgomery County, Md. (4513 Sangamore Road, Apt. 101, Washington, D.C. 20016) Filed May 27, 1966, Ser. No. 554,935 9 Claims. (Cl. 114-66.5)

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates to improved hydrofoil structures and retraction mechanisms therefor, and more particularly to improved hydrofoil structure and retraction mechanisms of increased strength.

The application of the principle of hydrofoils to ships is Well known in the prior art. Such ships have unique advantages unattainable by ships of more conventional design. The larger of this variety of craft are capable of sustained high speed through relatively rough seas, The sea keeping qualities at high speed are limited only by the distance which the ship is lifted above the mean water level. The high speed characteristics of these craft is attributable in the main to two of the most important characteristics of hydrofoil operation. The first characteristic is that the main lift or supporting force generated by the craft during hydrofoil operation is achieved by continuously submerged lifting elements. The submerged operation of these lifting elements results in the craft being relatively uneffected by surface variations in the water through which it travels. The second significant advantage attributable to hydrofoil operation is that the main body of the craft is not water wetted and therefore is not subjected to hydrodynamic resistance. The water wetted surface is thereby reduced to the relatively small area of the lifting portions of the hydrofoils themselves and to the necessary water surface piercing supporting struts.

The advantages of hydrofoil operation have been proved conclusively by research vehicles but the adaptation of these principles to practical craft, from either a military or commercial stand point, has been difficult. To have broad utility the hydrofoil craft must be capable of operation as a displacement ship without the large draft created by extended hydrofoils. This necessity has frustrated the attempt to keep the wetted surface and the total weight of the craft to a minimum and creates at least three problems. The first of these relates to the provision of suitable retraction mechanisms and hydrofoil arrangements that will permit the craft to convert from hydrofoil operation to displacement operation without below water line hydrofoil protrusions and without increased weight that would limit maneuverability and decrease cargo allowance. Secondly, the hydrofoil mechanisms and supporting struts of the prior art are excessively large and heavy because of the extra strength required to reduce undesirable strut deflections during turns and damage to the hydrofoil and strut from impacts with floating objects. Finally, the hydrofoil element design cannot be optimized because the most eflicient hydrofoil configuration for cruise speed operations is only marginally effective or not effective at all to produce the required lift for takeoff, that is, the lift required to raise the ship from its operation as a displacement craft to its operation as a hydrofoil craft.

The instant invention overcomes the disadvantages of the prior art and makes possible the construction of a hydrofoil craft that is both operable as a displacement vessel with none of the protrusions associated with unretracted or incompletely retracted hydrofoil elements. The structure of the instant invention provides the necessary additional lift to allow the efiicient transmission of opera:

tion from that of a displacement craft to that of a hydrofoil craft, and also provides additional rigidity in the hydrofoil supporting struts to reduce deflection during turns and damage due to the impact with objects, all without excessive weight increase.

It is therefore an object of the present invention to provide in a hydrofoil craft a hydrofoil support means with increased lateral stability and fixidity.

It is a further object if the invention to provide an improved hydrofoil retracting system.

It is an additional object of the invention to provide a hydrofoil craft with improved takeolf characteristics.

It is still a further object of the invention to provide in a hydrofoil craft, retractable hydrofoil supports that lock to the hull of the craft.

It is still another object of the invention to provide in a hydrofoil support an improved strut brace that provides both support and takeoff lift.

It is a final object of the invention to provide in a hydrofoil craft improved hydraulic retraction mechanisms.

These and other objects and many of the attendant advantages of the invention will be more readily understood by reference to the following detailed description of one specific embodiment thereof when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a side view of the craft embodying the concepts of the instant invention;

FIG. 2 is a front view of the craft showing the hydrofoil mechanism in its retracted position in dotted lines;

FIG. 3 is an end view of the strut and strut brace of one of the forward foils, showing the retraction mechanism and a preferred embodiment of the locking mechanism;

FIG. 4 is a top view of the actuating mechanism for the locking mechanism of FIG. 3;

FIG. 5 is a top view of alternative locking mechanism for the strut and strut brace of FIG. 3; and

FIG. 6 is a cross-sectional view of the strut brace shown in FIG. 3.

Referring now to the drawings there is shown in FIG. 1 a hydrofoil craft 10 embodying the concepts of the invention. The craft has a generally conventional displacement hull 12 which supports two forward foil and strut combinations, one of which is shown at numeral 14, and aft foil and strut combination shown at numeral 16. The aft foil and strut combination is shown to be retractable by a hydraulic cylinder 18, into a well on the center line of the hull 12. This well completely houses strut 2t and leaves only the foil section 22 protruding beyond the stern of the hull 12. Referring now to the forward strut and foil combination 14-, that combination is shown to comprise strut 24, foil section 26, and strut brace 28. This entire assembly is pivotable about pivot 30, which has forward and aft fairings 32 and 34 to reduce hydrodynamic resistance when the craft is operating as a displacement vessel. Brace 28 is shown to be swept aft from its point of attachment to strut 24 to its point of attachment 35 on hull 12. The purposes of the aft sweep of brace 28 will be explained more fully hereinafter. In addition to the foil supporting function of forward strut 24 it also supports forward propeller 36 and propeller nacelle 38. Power to propeller 36 is transmitted through forward strut 24 by suitable power transmission mechanisms not shown. Power is transmitted to the mechanism within forward strut 24 through a gear box contained within the aft pivot fairing 34.

In FIG. 2 there is shown an end view of the forward strut and brace combination 14 previously described with reference to FIG. 1, strut and foil combination 40. The strut and foil combination 40 is shown to comprise strut 42, foil 44, propeller 36, propeller nacelle 48, strut brace 50, and strut pivot 52 and is substantially identical in structure and operation to strut and foil combination 14. Also shown in FIG. 2, for both the strut and foil combination 14 and 40, are tie bars 54 and 56 respectively. The function of the tie bars 54 and S6 is to support the strut braces 28 and 50 when the foil and strut combinations are in their retracted position shown in dotted lines. As can be seen from the dotted line positions of the strut and foil combinations 14 and 40 the entire foil assembly is lifted and pivoted clear of the displacement water level 58 so as to not interfere with the vessels operation in this mode. The operating position of the strut and foil combinations is shown to retain the foils 26 and, in a position displaced from the horizontal. This displaced position is designed to augment the stability of the craft in roll as will be more fully explained hereinafter.

FIG. 3 is a detailed sectional View of the retraction mechanism and locking mechanism for strut and foil combination 14. Retraction is accomplished through the use of a first retraction cylinder 60 and a second retraction cylinder 62. Cylinder 60 is a double acting hydraulic cylinder attached at its upper end by pivot 64 to the hull 12 and its lower end to lever arm 66 through pivot 68. Cylinder 62 is also a double acting hydraulic cylinder which is attached at its inboard end to the hull. 12 through pivot 70 and attached at its other end cylinder 60 through pivot 72. This cylinder 62 is employed to achieve final retraction and locking in the retracted condition as will be more fully explained hereinafter.

The locking mechanism is generally indicated in FIG. 4 by numeral 74. A locking cylinder 76 is pivotally mounted through pivot 78 to bracket 80. Bracket 80 is affixed to the interior of hull 12. The piston rod extension 82 of cylinder 76 is pivotally mounted through pin 84 to lever arm 86 of eccentric locking member 88. The eccentric locking member is rotatably received in a watertight bearing not shown in the hull 12. The eccentric member carries eccentric extension 90 which is shown in FIG. 3 engaged with locking surface 92 of strut brace 28.

FIG. 4 shows, in full lines, the position of the locking eccentric in the locked position, the released position is shown in dotted lines. In this position the eccentric extension 90 of eccentric member 88 clears the locking surface 92 of strut brace 28 and allows it to rotate about pivot 30.

FIG. shows an alternative locking arrangement to that shown in FIGS. 3 and 4. In this embodiment strut brace 28has two conical recesses 85 and 87 at its inboard end. The portion of the strut brace with the conical recesses is received in the operative position by a locking bracket 89 mounted on hull 12. This locking bracket supports two hydraulic cylinders 91 and 94, which contain pistons 96 and 98 respectively. Pistons 96 and 98 carry conical extensions and 102 respectively which are sized so as to snugly fit within the conical recesses 85 and 87 in strut brace 28 as shown by their dotted line position in FIG. 5.

It is to be understood that the description of the locking mechanism both in FIGS. 3 and 4 and FIG. 5 for strut brace 28 is equally applicable to substantially identical strut brace 50.

Referring now to FIG. 6 it can be seen that strut brace 28 has a hydrofoil configuration. This configuration is employed both to reduce the hydrodynamic resistance of the strut brace during displacement operations with the strut and brace in the locked position and more importantly to provide improved takeoff performance. The takeoff performance is improved through the incorporation in the strut braces 28 and 50 a hydrofoil configuration having, for example, camber or a positive angle of attach, or both.

The unique advantages of the hydrofoil mechanisms of the invention will be most evident from a description of their operation in normal use. The craft may be assumed to be docked with both the forward and aft foils retracted to their minimum draft condition, that is, with aft strut and foil combination 16 contained within the housing at the stern of the craft and with forward strut and foil combinations 14 and 40 raised as indicated by their dotted line position in FIG. 2. This condition not only reduces the overall draft of the craft but avoids below water line protrusions beyond the vessels hull and thereby permits increased maneuverability and minimizes the possibility of damage. Because the craft described in the specific embodiment employs foil mounted propulsion means which are inoperative when in the retracted position, auxiliary propulsion means must be provided. This auxiliary propulsion source may take the form of a stern mounted propeller drive unit of comparatively small size and must be sufliciently powerful only to propel the ship at maneuvering speeds while reaching deeper water so that the foils may be lowered. As an alternative to a propeller drive unit a water jet unit may be provided supplied either from the main ship power plant or an auxiliary power plant. The auxiliary propulsion means propels the craft under its own steerage and power from the dock side and from the harbor toward deeper water. When deeper water is reached the stern strut and foil unit is lowered so as to provide steerage power while the forward struts are being lowered. This rear strut lowering is accomplished through the actuation of cylin der 18 which forces the aft foil strut 20 firmly against strut thrust pad 104. Locking means not shown hold the aft foil strut in its extended position. Forward strut lowering is then begun and may best be described with reference to FIG. 3. The second retraction cylinder 62 is first activated to force the strut pivot and its retraction cylinder 60 over center. At this stage retraction cylinder 60 may be actuated and strut 24 forced to its operative position. In this position strut brace 28 is located immediately adjacent the locking eccentric 78 which has been maintained in the open position. To lock the strut foil combination in its lowered position, cylinder 76 is actuated to rotate the eccentric member 88 into the locking position where the eccentric extension 82 firmly engages mating face 84 on strut 28.

With all the foils in place power may be applied through the power transmission gear boxes and associated shafting and increased forward way developed. At this stage the craft isstill operating as a displacement vessel and operation in this mode continues until the lift developed by the foils is sufiicient to lift the hull 12 clear of the water surface. With conventional hydrofoil craft this lifting or takeoff stage is a difi'icult phase because considerable forward way is necessary before the main foils develop suflicient lift to raise the vessel clear of the water as indicated in FIG. 1 by the takeoff water line 55. In some instances the power requirements necessary to achieve this lifting effect are in excess of those which are capable of being utilized at cruise. This result obtains because of the relatively small lifting area of the main foils due to their design for most efiicient operation at high speed. In the craft of the invention however, takeoff is facilitated by the provision of lifting surfaces on strut braces 28 and 50. These lifting surfaces are effective to provide additional lift in the early phases of takeoff and thereby raise a considerable portion of the crafts hull above the water level. With the reduced wetted surface thus obtained the acquisition of necessary speed for full'hydrofoil operation is achieved with lower power because of the reduced hydrodynamic drag caused by hull immersion. When full hydrofoil operation is achieved the lifting surfaces of the strut braces are completely clear of the water surface and thereby contribute no parasite drag to the crafts hydrofoil operation.

It is of course advantageous to reduce the size and number of water surface penetrating members to a minimum. This ideal situation has been frustrated in the past by the necessity for stiffening and bracing of the hydro= foil members and their supporting struts. In a hydrofoil craft with single strut supported foils as in the invention but without the additional bracing provided by strut braces 28 and 50 the bending stresses caused by violent maneuvers and heavy seas would so flex the supporting struts so as to either cause controllability problems or strut failure. In addition such single strut supported foils would be especially subject to object impact damage caused by collision with floating objects in the path of the hydrofoil strut member. In the instant invention these strength deficiencies of prior art single strut supported foil members are obviated by the unique strut brace member of the invention. As can be best seen in FIG. 2 the strut braces are athxed to the struts 24 and 42 at a considerable distance from the struts attachment point to the hull through pivots 30 and 52. This spacing from the main attachment point reduces bending moments and allows the transfer of a considerable portion of the stress and shock directly to the hull at the points of locking attachment for strut braces 28 and 50. This additional support is especially important when the ship pitches violently either due to intentional maneuvers or heavy seas. The. increased resistance to object impact damage of the forward foil and strut members is accomplished by raking the strut brace members aft from their point of attachment to the strut member, that is, the strut brace locking attachment points to the hull are positioned considerably aft of the center line of attachment to struts 24 and 42. Thus a considerable portion of impact stress is transferred through the rigid strut brace member directly to the locking attachment points of the strut brace members and not as in prior art devices to the pivot points 30 and 52.

During hydrofoil operations the stability of the ship in roll is augmented by orientation of the foil members relative to the horizontal. The stabilizing effect is similar to that caused by aircraft Wing dihedral. When the craft rolls, the foil in the direction of roll becomes more horizontal and its lift component in the vertical direction increases which tends to right the craft. The return of the ship to operation as a displacement vessel and retraction of the foils is accomplished by a procedure substantially the reverse of the technique of transferring from displacement operation to operation as a hydrofoil. The crafts speed is reduced and it slowly settles onto the hull 10 until it is resting on the hull and retraction can begin. The forward foils are first retracted and this retraction is begun by unlocking the strut brace locking members on strut braces 28 and 50. This unlocking is accomplished in the case of the locking mechanism shown in FIGS. 3 and 4 by the retraction of the piston member and piston extension 82 of hydraulic cylinders 76. This retraction rotates ececntric locking member 78 and eccentric extension 82 clear the locking portion 84 of strut brace 82 leaving it free to rotate about its pivot. Similarly the locking mechanism of FIG. 5 is released by the application of retracting pressure to hydraulic cylinders 91 and 94 whereby the pistons and piston extensions 100 and 102 are retracted from the conical recesses 85 and 87 in strut brace member 28.

It is to be understood that the locking mechanisms shown in the preferred and alternate embodiments are only two of many possible solutions to the locking .requirement. Other locking mechanisms may be employed with the hydrofoil strut member of the invention and modifications of the disclosed locking mechanisms are within the scope of the invention. For example, the motor power to the retraction mechanisms in both FIGS. 3 and 4 and in FIG. 5 may be electrical rather than hydraulic, i.e., servomotors.

Returning now to the operation of the craft, with the strut and foil combinations 14 and 40 unlocked from the strut brace locks, retraction by hydraulic cylinders shown in FIG. 3, can be begun. Initial retraction is through the first cylinder. This cylinder provides the main retracting force to rotate strut in foil combination 14 about pivot 30 until the strut and foil combination is in a position well above the water line. At this position the lever arm of cylinder relative to the axis of rotation about pivot 30 becomes quite small and final retraction is accomplished by the activation of secondary cylinder 62 to completely withdraw the hydraulic retraction mechanisms within the well 106 provided Within hull 12. The forward foils are then in the dotted line position shown in FIG. 2 and retraction of the stem or aft foil may begin. Simultaneously with the beginning of retraction of aft foil and strut combination 16 the auxiliary power source is again activated to provide steerage way so that the craft may be under control at all times, minimizing the possibility of damage to the retracting foils due to unexpected pitches from the prevailing sea conditions. When aft foil strut 20 is completely contained within the well in hull 10 by the action of hydraulic cylinder 18 the craft is again able to operate as a displacement ship and will continue in this mode to dock side.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An improved hydrofoil craft having at least two forward foils and at least one aft foil, said foils being supported by strut members extending from the hull of said craft to said foil members, wherein the improvement comprises:

strut brace members having the first ends thereof attached at a point on said strut members intermediate the ends of said strut members, and releasably attached at the second ends thereof to the hull of said craft;

releasable locking means on the hull on said craft for releasably locking the second ends of said strut brace members to the hull of said craft during the hydrofoil operations of said craft;

each of said releasable locking means including a locking member and actuating means; and

retraction means for raising and lowering said forward strut members and foils between an operative position and a retracted position.

2. The improved hydrofoil craft of claim 1 wherein said forward struts retract by pivoting about hull mounted pivots on the port and starboard sides of said craft.

3. The improved hydrofoil craft of claim 2 further including tie bars on said forward strut and foil combinations extending from said strut to the inboard end of said strut brace closely adjacent to the point of attachment to said locking means.

4. The improved hydrofoil craft of claim 1 wherein the point of attachment to said hull for said strut braces is substantially aft of the point of attachment to said strut.

5. The improved hydrofoil craft of claim 1 wherein the said locking means comprises:

a hydraulic cylinder and a piston rod with a piston rod extension mounted on the interior of said hull;

an eccentric locking member rotatably mounted through said hull and having an eccentric locking extension engaged with a mating surface on said strut brace in the operative position;

said hydraulic cylinder piston extension being pivotally connected to said eccentric member.

6. The improved hydrofoil craft of claim 1 where said locking means comprises:

locking pin means receivable within a recess in said strut brace; and

actuating mans to force said locking pin means within said recess in said strut brace in the operative position and to withdraw said locking pin means in the retracted position.

7. The improved hydrofoil craft of claim 2 wherein said retraction means comprises:

a first hydraulic cylinder for each of said forward foil and strut combinations mounted on said hull at one end thereof and pivotally connected to a lever arm at the other end thereof;

a said lever arm being mounted on said strut at a distance,

spaced from said pivot; and

a second hydraulic cylinder for each of said forward foils mounted to said hull at one end thereof and pivotally connected to said first retraction cylinder at the other end thereof at a point intermediate the ends of said first hydraulic cylinder.

8. The improved hydrofoil craft of claim 1 further including:

a well within the hull of said craft;

a single aft strut and foil member pivotally mounted within said well; and

retraction means for raising and lowering said aft strut and foil member from an operative position to a re- 20 tracted position, the strut portion of said strut and foil member being substantially completely contained within said well in said retracted position.

said strut and foil member being pivotally mounted within said well; and retraction means for raising and loweringsaid aft strut and foil member from an operative position to a re-- tracted position;

said strut and foil member in said retracted position having the strut portion thereof substantially completely contained within said well and the foil portion thereof in close proximity to the stern of said craft.

References Cited UNITED STATES PATENTS 3,081,728 3/1963 Wilterdink et al. 114-66.S 3,199,483 8/1965 Ellzey 114-665 MILTON BUCHLER, Primary Examiner.

A. H. FARRELL, Assistant Examiner. 

1. AN IMPROVED HYDROFOIL CRAFT HAVING AT LEAST TWO FORWARD FOILS AND AT LEAST ONE AFT FOIL, SAID FOILS BEING SUPPORTED BY STRUT MEMBERS EXTENDING FROM THE HULL OF SAID CRAFT TO SAID FOIL MEMBERS, WHEREIN THE IMPROVEMENT COMPRISIES: STRUT BRACE MEMBERS HAVING THE FIRST ENDS THEREOF ATTACHED AT A POINT ON SAID STRUT MEMBERS INTERMEDIATE THE ENDS OF SAID STRUT MEMBERS, AND RELEASABLY ATTACHED AT THE SECOND ENDS THEREOF TO THE HULL OF SAID CRAFT; RELEASABLE LOCKING MEANS ON THE HULL ON SAID CRAFT FOR RELEASABLY LOCKING THE SECOND ENDS OF SAID STRUT BRACE MEMBERS TO THE HULL OF SAID CRAFT DURING THE HYDROFOIL OPERATIONS OF SAID CRAFT; EACH OF SAID RELEASABLE LOCKING MEANS INCLUDING A LOCKING MEMBER AND ACTUATING MEANS; AND RETRACTION MEANS FOR RAISING AND LOWERING SAID FORWARD STRUT MEMBERS AND FOILS BETWEEN AN OPERATIVE POSITION AND A RETRACTED POSITION. 